Flood watches cover Phoenix to Four Corners as Halloween storms roll in

Phoenix first: A flood watch covers metro Phoenix, rural Maricopa County and northwest Pinal County until 6 p.m. Friday, with rain rates of up to 1 to 2 inches an hour possible and localized totals of 1 to 2 inches, the Phoenix office said. Forecasters there said a few storms could turn strong, with hail and gusty winds possible. Watches for Superior, Globe-Miami and the Tonto Basin, and for Yavapai County and northern Gila County, run until 10 p.m.; the Flagstaff office warned of high flows on waterways that flooded as recently as last week.

Round two over flooded ground: Starting late Saturday night, watches cover southwest Colorado's Animas and San Juan basins and southeast Utah through Monday morning, where the Grand Junction office expects 1 to 3 inches on soils still saturated from recent rain and flooding. Northwest New Mexico, including the Chuska Mountains and the Northwest Plateau, is under a watch for 1 to 2 inches west of the Continental Divide. The Albuquerque office said areas are still recovering from the last flood, adding: "River rises are likely, but rises are not expected to be as high as the last flood event." Coconino, Navajo and Apache counties in Arizona, including the Navajo Nation, face 1 to 3 more inches from 11 p.m. Saturday to 5 a.m. Monday. Last week's flooding forced rescues and evacuations around Farmington, N.M., and Bluff, Utah (see /article/us-four-corners-flooding-rescues).

Parks and canyons: In southern Utah, a watch from late Saturday night through Sunday evening covers Zion, Capitol Reef and Bryce Canyon country, Lake Powell and lower Washington County; the Salt Lake City office said slot canyons and backcountry roads are likely to become impassable. In southern Arizona, the Tucson office's watch runs Saturday evening through late Sunday night for Tucson, Nogales, Sierra Vista and Cochise County, with half an inch to an inch in the valleys and 1 to 2 inches or more in the mountains. The Las Vegas office added northwest Arizona, including the Hualapai Mountains, where more than an inch is possible.

Southern California too: The San Diego office expects widespread rain to start Saturday evening and turn moderate to heavy late Saturday night into Sunday morning before ending Monday morning. The Los Angeles office said the heaviest rain should fall south of Los Angeles County but noted that computer models still disagree. Rain on Halloween is rare in San Diego: the Fox Forecast Center counted only nine rainy Halloweens there since 1850, the last in 1987.

Elsewhere: Fox Weather said storms could touch more than 20 states on Halloween, with 2 to 3 inches of rain possible in parts of southern Alabama and Georgia and up to 5 inches in isolated spots. The Northeast should stay dry Saturday in the low to mid 60s before rain arrives Sunday. In West Texas, Midland closed low-water crossings under a flood watch this week, the Midland Reporter-Telegram reported.

How the weekend lines up: Friday afternoon and evening, central Arizona, including Phoenix until 6 p.m. and the mountains to the north and east until 10 p.m. Saturday evening, southern and northwest Arizona and Southern California's rain begin. Late Saturday night into Sunday, the heaviest rain hits northern Arizona, southern Utah, southwest Colorado and northwest New Mexico. Monday morning, most watches expire, though the Pueblo office's watch for Colorado's San Luis Valley runs through late Tuesday.

What's still unknown: Exactly where the heaviest bands set up, especially in Southern California, where models disagree, and whether any watches get upgraded to flash flood warnings. Forecasters in Albuquerque expect river rises below last week's peaks, but they have not issued crest forecasts for this round. A flood watch means conditions favor flooding; a warning means it is happening or imminent. Check local forecasts at weather.gov.

Sourcing: watch areas, times and rain amounts are from National Weather Service alerts and forecast discussions issued Friday, Oct. 30, by its Phoenix, Flagstaff, Tucson, Las Vegas, Salt Lake City, Grand Junction, Albuquerque, Pueblo, San Diego and Los Angeles offices. National details on other states are from Fox Weather and AccuWeather; the Midland item is from the Midland Reporter-Telegram. Arizona times are Mountain Standard Time, which matches Pacific time this weekend. Watches can be extended, upgraded to warnings or canceled. Photos are file images, not from this storm.